Setscrew retention in connector block for implantable medical device

ABSTRACT

A header assembly for coupling a medical electrical lead to a medical stimulating device includes a header having a first bore for receiving a proximal terminal pin of the lead. A connector block coupled to the header has a second bore aligned with the first bore and a tapped bore transverse of, and in communication with, the second bore, and the assembly includes a setscrew with mounting threads of defined length threadedly engaged with the tapped bore. The tapped bore defines a tapped region adjacent the second bore, and a smooth bore region which is longer than the length of the threaded portion of the setscrew to prevent the setscrew from being completely backed out of the tapped bore.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 11/072,805, filed Mar. 3, 2005, titled “SetscrewRetention in Connector Block for Implantable Medical Device.”

FIELD OF THE INVENTION

This invention relates to headers for coupling a lead for a tissuestimulating devices, such as a cardiac pacemaker or implantablecardioverter-defibrillator, to a pulse generator, and more particularlyto a mechanical connector which incorporates a unique setscrew retentionconstruction.

BACKGROUND

Implantable medical tissue stimulators including pacemakers,defibrillators and neural stimulators are used to stimulate tissue suchas cardiac tissue or spinal cord tissue with electrical pulses. Suchtissue stimulators are now quite common and typically include ahermetically sealed housing or can containing an electronic circuit andpower supply for producing electrical impulses under control of aprogrammed microprocessor. The pulse generator is connected to targettissue by means of a suitable medical lead. Such leads typically includean elongated flexible lead body having a proximal end and a distal end.Disposed at the distal end of the lead are one or more tissue contactingelectrodes. The electrodes are connected by wires running through thelead body to associated contacts on a terminal pin at the proximal endof the lead.

The proximal lead terminal pin is adapted to be inserted into alongitudinal bore formed in a header of the stimulating pulse generator.Contained within the header are one or more conductive connector blocksthat are connected to feedthrough pins that pass through hermetic sealsto join with input and/or output nodes of the electronic circuitcontained within the housing. The connector blocks will typically haveapertures formed therethrough in alignment with the bore of the header,allowing the proximal lead terminal pin to be inserted through them. Tolock the lead in place, the connector blocks will typically include athreaded bore that extends transverse to the longitudinal direction ofthe bore in the header. Setscrews are inserted into these threaded boresand tightened down against contact areas on the proximal lead terminal.In prior art connector block designs, from time to time the setscrew isaccidentally backed out completely from the block and could not bere-inserted in to the block. Another equally problematic situationoccurs when the lead is not inserted in the connector block and thesetscrew is advanced to the extent that it falls into the longitudinalbore of the block which is an extension of the longitudinal leadreceiving bore of the header.

U.S. Pat. No. 5,989,077 to Mast et al. provides an example of a headerassembly of the type which the present invention seeks to avoid.Specifically, the header assembly serves for coupling a cardiac lead toa cardiac stimulator and employs a setscrew threadedly coupled to aconnector housing of the header assembly but without provision forretaining it in place so that it neither backs out of the tapped bore inwhich it is received or advances too far in the absence of an end of alead which it is intended to engage.

In U.S. Pat. No. 5,000,177 to Hoffmann et al., an implantable system isprovided in which setscrews are confined within bores of the connectorblock against advancing too far but, not with standing the provision ofplug seals over their heads, are capable of being backed away from theirthreaded condition.

In U.S. Patent Application Publication US 2004/0225334 to Persuitti etal., a connector block and its associated locking setscrew for animplantable electronic tissue stimulating device are designed toeliminate thread damage to the setscrew which is a cause of the setscrewbecoming stuck in the connector block. In this disclosure, there is noconcern presented for the problem addressed by the present invention.

It was in light of the foregoing that the present invention wasconceived and has now been reduced to practice.

SUMMARY

A header assembly for coupling a medical electrical lead to a medicalstimulating device includes a connector block coupled to the header, theconnector block including a first bore to receive a terminal pin of alead and a tapped bore in communication with the first bore. Theassembly also includes a setscrew with mounting threads of a definedlength. The tapped bore has a tapped region proximate the first bore,and a smooth bore region next to the tapped region which is longer thanthe length of the threaded portion of the setscrew. Thus, when aclinician backs out the setscrew, the threads of the setscrew willdisengage from the tapped region of the tapped bore and reside in thesmooth bore region. Because the setscrew is disengaged from the tappedregion, the clinician will be unable to further unscrew the setscrewfrom the tapped bore, thereby retaining the setscrew within the tappedbore. Furthermore, with the setscrew residing in the smooth bore region,the clinician will have an indication that the setscrew has beensufficiently unscrewed for removal or insertion of the proximal pin of alead.

Other and further features, advantages, and benefits of the inventionwill become apparent in the following description taken in conjunctionwith the following drawings. It is to be understood that the foregoinggeneral description and the following detailed description are exemplaryand explanatory but are not to be restrictive of the invention. Theaccompanying drawings which are incorporated in and constitute a part ofthis invention, illustrate one of the embodiments of the invention, andtogether with the description, serve to explain the principles of theinvention in general terms. Like numerals refer to like parts throughoutthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present invention areexplained in the following description, taken in connection with theaccompanying drawings, wherein:

FIG. 1 is an exploded perspective view of an implantable medical deviceembodying the present invention, illustrating a sealed pacemaker housingand its associated header assembly, and an associated lead ready forinsertion into a receiving channel of the connector;

FIG. 2 is a side elevation view of a connector block according to oneillustrative embodiment;

FIG. 3 is a top plan view of the connector block illustrated in FIG. 2;

FIG. 4 is a cross section view taken generally along line 4—4 in FIG. 3;

FIG. 5 is a detail cross section view, in elevation, illustrating ingreater detail a portion of FIG. 4;

FIG. 6 is a perspective view of a setscrew according to one illustrativeembodiment;

FIG. 7 is a top plan view of the setscrew illustrated in FIG. 6;

FIG. 8 is a side elevation view of the setscrew illustrated in FIGS. 6and 7;

FIG. 9 is a cross section view taken generally along line 9—9 in FIG. 8;

FIG. 10 is a side elevation view in section illustrating one relativeposition of the combination of the connector block and the setscrew;

FIG. 11 is a side elevation view in section illustrating anotherrelative position of the combination of the connector block and thesetscrew;

FIG. 12 is an exploded perspective view of another embodiment of aconnector block and setscrew;

FIG. 13 is a cross-sectional view of the connector block and setscrew ofFIG. 12 in an assembled state; and

FIG. 14 is a cross-sectional view similar to FIG. 13 and showing anotherillustrative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turn now to the drawings and, initially to FIG. 1 which generallyillustrates, diagrammatically, an elevation view of a header assembly orconnector system 40 for a sealed implantable medical device such as acardiac stimulation device 16, possibly in the form of a pacemaker.Although the present invention will be described with reference to theembodiments shown in the drawings, it should be understood that thepresent invention can be embodied in many alternate forms orembodiments. In addition, any suitable size, shape or type of elementsor materials may be used.

In order to appreciate the advantages of the present invention, it willhelp first to have a basic understanding of the manner in which themechanical and electrical connection functions are carried out in knowncardiac stimulation devices, a pacemaker here being exemplary. The maincomponents associated with the connection function of such knownpacemakers are shown diagrammatically in FIG. 1 but apply to the presentinvention as well. A pacemaker 10 electrically includes a battery 14that powers electrical circuits 12. The pacemaker electrical circuits 12and battery 14 are mechanically enclosed and hermetically sealed in asuitable housing 16. Typically, this housing or case 16 is shaped toinclude a flat side or platform 20 to which a suitable header assembly22 can be mounted. At least one feedthrough terminal, 18, in electricalcontact with the electrical circuits 12, passes through the case orhousing 16 and protrudes beyond the platform 20. This feedthroughterminal 18 is electrically isolated from the case 16. A platinum wire24, or other suitable conductive element, connects the terminal 18 to aconductive connector block 26 that is fitted within the header assembly22. A pacemaker lead 28 having a proximal electrode or terminal pin 30connects to the pacemaker electrical circuits by inserting the terminalpin 30 into a receiving channel or first bore 31 of the header assembly22 until the terminal pin 30 is in contact with the connector block 26by way of a block receiving channel or second bore 31 a. A setscrew 32is then securely tightened using a tool 34 such as a torque wrench tofirmly hold the electrode 30 in both mechanical and electricalconnection with the connector block 26. A septum, not shown buttypically having the construction generally described in commonlyassigned U.S. Pat. No. 5,509,928 issued Apr. 23, 1996 to Acken, may beplaced over the setscrew 32 in order to prevent body fluids from seepingthrough the setscrew hole. Further, sealing ribs or ridges 36 on theconnecting end of the pacemaker lead are designed to tightly engage theinside edges of the receiving channel 31 in order to prevent any bodyfluids from entering into the receiving channel 31 once the connectingend of the lead has been inserted into the header assembly 22.

While the descriptions presented in the prior art vary greatly relativeto, for example, different types of locking mechanisms for performingthe mechanical connection function, or different types of arrangementsfor performing the electrical feedthrough function, including the use ofbipolar or multiple pacemaker leads, all such systems include the use ofa pre-molded or cast header assembly 22 that is bonded to a sealedpacemaker housing 16 in which the electrical circuits are located.

Typically, prior art header assemblies 22 are cast in place from epoxyto the platform 20 of the pacemaker or, using more recent technology, apre-molded header assembly may be mounted to the platform using asuitable sealing and bonding agent. Further, once the electricalconnection is made from the terminal post 18 to the connector block 26,and the header assembly is attached to the housing, all remaining voidswithin the header 22, not including the receiving channel 31 into whichthe proximal end of the pacemaker lead 28 is to be inserted, must befilled with a suitable filler material, such as a two-component epoxy orsilicone rubber.

It was earlier mentioned that the focus of the present invention is toprovide retention features for the setscrew for a pair of potentialproblematic situations. By using the teachings of the invention, thesetscrew 32 will not be able to be advanced all the way in or backed outcompletely from the connector block. For an explanation of the specificsof the invention, while continuing to view FIG. 1, turn now also toFIGS. 2 to 9.

As earlier noted, the connector block 26 (see FIGS. 2, 3, 4, and 5) issuitably coupled to the header assembly 22 and has the second bore 31 aaligned with the first bore 31 and a tapped bore 42 provided in theconnector block 26 has an axis transverse of, and in communication with,the second bore. Associated with the connector block is the setscrew 32(see FIGS. 6, 7, 8, and 9) which extends from a mounting shank 44 at ahead end 46 to mounting threads 48 of a defined length 49 adjacent a tipend 50. The tapped bore 42 of the connector block 26 has first andsecond tapped regions 52, 54, respectively, spaced by a smooth boreregion 56 which is longer than the defined length 49 of the mountingthreads 48 of the setscrew 32.

Turn now to FIGS. 10 and 11 in addition to the prior figures. FIGS. 10and 11 illustrate another embodiment of the connector block 26 and inthis embodiment, the connector block is indicated by reference numeral26 b and all other components in this connector block embodiment areindicated by similar reference numerals with the suffix “b”. Thesetscrew 32 is threadedly engaged with the tapped bore 42, 42 b. Thehead end 46 of the setscrew 32 is formed, as at 57, to engageablyreceive the tool 34 (FIG. 1) for tightening the setscrew into engagementwith the proximal terminal pin 30 of the medical electrical lead 28 and,alternatively, for withdrawing the setscrew from engagement with theproximal terminal pin of the medical electrical lead. With particularattention to FIGS. 10 and 11, it is seen that the connector block 26 bhas a square shoulder 58 b at the interface between the second tappedregion 54 and the second bore 31 b engageable with a shoulder 60 of thesetscrew 32 spaced from the tip end 50 to prevent the setscrew fromadvancing farther into the second bore. It will be-understood that, inthe instance of the connector block 26 of FIGS. 4 and 5, if the diameterof the bore 31 a is larger than the length of the setscrew 32, thesetscrew could advance until it deleteriously falls into the bore 31 a.The altered construction of the connector block 26 b illustrated inFIGS. 10 and 11 prevents this occurrence.

With this construction, as the setscrew 32 is tightened into engagementwith the tapped bore of the connector block, it has already beenthreaded through the first tapped region 52, 52 b and resides within thesmooth bore region 56, 56 b, and then becomes threadedly engaged withthe second tapped region 54, 54 b until the tip end 50 is firmly engagedwith the proximal terminal pin 30 of the medical electrical lead 28extending through the first bore 31 and into the second bore 31 a, 31 b.It will be appreciated that with the tip end 50 of the setscrew 32engaged with the proximal terminal pin 30, a space will exist betweenthe shoulder 60 of the setscrew and the square shoulder 58 b of theconnector block 26 b. Should the proximal terminal pin 30 be removedfrom the bore 31 b, the setscrew 32 can then be advanced but only to theextent that the shoulder 60 engages the square shoulder 58 b and fartheradvance of the setscrew is halted.

Although the setscrew 32 can be loosened from its engagement with theproximal terminal pin 30, it can no longer leave the confines of thetapped bore 42, 42 b because the tool 34 used for its initialadvancement into the connector block 26, 26 b is incapable of applyingan oppositely directed force for its removal from the connector block.More specifically, the defined length 49 of the mounting threads 48 ofthe setscrew 32 is shorter than the length of the smooth bore region 56,56 b. With the setscrew freely residing within the smooth bore region,it would be necessary to pull the setscrew toward the first tappedregion 52, 52 b but the tool 34 has no such capability. Hence, once thesetscrew 32 is advanced into the smooth bore region 56, 56 b, it remainsin the tapped bore 42, 42 b for the life of the connector block unlessextraordinary steps are taken.

Referring now to FIGS. 12 and 13, yet another embodiment of a connectorblock 100 is shown. Connector block 100 is formed having the first bore102 and transverse, tapped bore 104 that receives a setscrew 106,similar to the embodiments described above. However, tapped bore is notformed having two tapped regions, but instead has only a single tappedregion 108 adjacent the distal end of tapped bore 104. Rather than beingthreaded, proximal end of tapped bore 104 includes a retaining washer110 that defines a relatively narrow opening. Retaining washer 110 isreceived in a countersunk portion of tapped bore 104 defining a recess111 and may either be press fit into recess 111, or placed in recess 111and then spot welded to remain in place, or any other suitable method ofsecuring retaining washer 110 in recess 111.

Thus, retaining washer 110 provides a shoulder that prevents setscrew106 from being removed from tapped bore 104. As with the above-describedembodiments, tapped bore 104 includes a smooth bore region 112 whoselength is longer than the threaded portion of setscrew 106. As such,setscrew 106 cannot be unscrewed and backed out of tapped bore 104,because the threads will disengage from the tapped region 108 whilesetscrew still resides in tapped bore 104. Moreover, retaining washer110 prevents setscrew 106 from exiting tapped bore 104.

As described above, in one embodiment the distal end of tapped bore 104is preferably formed with a shoulder or tapering threads (not shown) toprevent setscrew 106 from being over-advanced into the first bore 102.

FIG. 14 depicts still another embodiment of a connector block 200 andsetscrew 202. In this embodiment, a first bore 204 is provided to acceptthe proximal pin of a lead, and transverse bore 206 is provided toreceive setscrew 202. Transverse bore 206 extends from one end ofconnector block 200 to the other end, and differs in that regard fromthe other embodiments described herein. Furthermore, transverse bore 206defines a tapped region 208 that extends from the bottom of block 200into the upper portion of block 200, and then transitions to a smoothbore region 210 similar to the smooth bore regions of the otherembodiments described herein.

Connector block 200 is further formed having an integral shoulder 212 atthe upper end of block 200, which replaces the retaining washer 110shown in FIGS. 12 and 13.

Thus, in the embodiment of FIG. 14, setscrew 202 is installed throughthe bottom of block 200. Once setscrew is threaded upwardly through thetransverse bore 206 until it resides in the smooth bore region 210 (asshown in FIG. 14), setscrew 202 is retained within transverse bore 206by shoulder 212. A proximal terminal pin may then be inserted into firstbore 204, and setscrew 202 may be advanced through transverse bore 206until setscrew 202 engages the terminal pin. To remove the terminal pinfrom connector block 200, setscrew 202 is unscrewed, either partiallyuntil the terminal pin may be removed, or unscrewed completely untilsetscrew 202 resides in the smooth bore portion of transverse bore 206.In either case setscrew 202 is retained within connector block 200 andthere is no concern of setscrew 202 being removed from connector block200.

It should be understood that the foregoing description is only ofillustrative embodiments. Various alternatives and modifications can bedevised by those skilled in the art without departing from theinvention. Accordingly, the present invention is intended to embrace allsuch alternatives, modifications and variances which fall within thescope of the appended claims.

1. A header assembly for coupling a medical electrical lead to an implantable medical device, the header assembly comprising: a connector block coupled to the header and having a first bore for receiving a proximal terminal pin of the medical electrical lead and a tapped bore in communication with the first bore, the tapped bore defining proximal and distal ends; and a setscrew comprising mounting threads of a defined length; wherein the tapped bore defines a distal tapped region and a smooth bore region proximal of the distal tapped region, the smooth bore region longer than the defined length of the mounting threads; and wherein the tapped bore further defines a proximal tapped region proximal to the smooth bore region.
 2. A header assembly as set forth in claim 1 wherein one end of the setscrew is formed to engageably receive a tool for tightening the setscrew into engagement with the proximal terminal pin of the medical electrical lead and, alternatively, for withdrawing the setscrew from engagement with the proximal terminal pin of the medical electrical lead.
 3. A header assembly as set forth in claim 1 wherein the connector block has a square shoulder at the interface between the distal tapped region and the first bore.
 4. A header assembly as set forth in claim 3 wherein the setscrew defines a tip end that extends distally from the mounting threads and configured to extend into the first bore.
 5. A header assembly as set forth in claim 1 wherein the connector block defines a shoulder at the interface between the proximal tapped region and the smooth bore region.
 6. A header assembly as set forth in claim 1 wherein the distal tapped region extends to an outer surface of the connector block.
 7. A connector system for use with a sealed implantable medical device having a medical electrical lead receiving bore for slidably receiving a proximal terminal pin of an electrical lead, the lead receiving bore having an open end for receiving the proximal pin and a closed end, the connector system comprising: a pulse generator operative to generate electrical stimuli; a sealed housing containing the pulse generator; a header having a first bore for receiving the proximal terminal pin of the medical electrical lead; a connector block coupled to the header and having a second bore aligned with the first bore and a tapped bore transverse of, and in communication with, the second bore; and a setscrew comprising a mounting shank at a head end and mounting threads of defined length adjacent a tip end; wherein the tapped bore has a first tapped region and a smooth bore region which is longer than the defined length of the mounting threads of the setscrew; and wherein the tapped bore further defines a second tapped region proximal to the smooth bore region.
 8. A header assembly as set forth in claim 7 wherein the head end of the setscrew is formed to engageably receive a tool for tightening the setscrew into engagement with the proximal terminal pin of the medical electrical lead and, alternatively, for withdrawing the setscrew from engagement with the proximal terminal pin of the medical electrical lead.
 9. A header assembly as set forth in claim 7 wherein the connector block has a square shoulder at the interface between the second tapped region and the smooth bore region.
 10. A header assembly as set forth in claim 7 wherein the distal tapped region extends to an outer surface of the connector block.
 11. A header assembly as set forth in claim 7 wherein the connector block has a square shoulder at the interface between the first tapped region and the smooth bore region.
 12. In combination, a connector block and a lead-locking setscrew for use in a header of an implantable pulse generator, the header having a first bore for receiving a proximal terminal pin of a medical electrical lead, comprising: the connector block coupled to the header and having a second bore aligned with the first bore and a tapped bore transverse of, and in communication with, the second bore; and a setscrew comprising mounting threads of defined length; wherein the tapped bore has at least one tapped region and a smooth bore region which is longer than the defined length of the mounting threads of the setscrew; and wherein the tapped bore further defines a proximal tapped region proximal to the smooth bore region.
 13. A header assembly as set forth in claim 12 wherein the head end of the setscrew is formed to engageably receive a tool for rotating the setscrew.
 14. A header assembly as set forth in claim 12 wherein the connector block has a square shoulder at the interface between the tapped region and the second bore.
 15. A header assembly as set forth in claim 12 wherein the connector block defines a shoulder at the interface between the proximal tapped region and the smooth bore region.
 16. A header assembly as set forth in claim 12 wherein the distal tapped region extends to an outer surface of the connector block. 